Blind rivets or fasteners are of the type used when only one side of the work-piece is accessible. In such fasteners, a stem and a sleeve are inserted as a unit into aligned openings in work-pieces. The sleeve typically has a tail which engages the blind side of the work-pieces and a head which engages the side of the work-pieces which is accessible. A stem tail extending beyond the sleeve head is pulled from the accessible side of the sleeve causing a head on the stem, protruding beyond the sleeve tail to be drawn against the sleeve tail to deform it and fasten them together by either flaring the sleeve into the holes through the work-pieces, or creating a bulb on the blind side of the work-pieces, or a combination of the two. Once the sleeve has deformed, the work-pieces stay secured together, sandwiched between the head of the sleeve on the accessible side of the work-pieces and the sleeve deformation within the holes and on the blind side of the work-pieces. At the completion of fastener installation, the stem tail typically breaks at a predetermined location near the head of the sleeve, allowing for removal of the excess stem portion protruding from the sleeve.
Many types of tools have been developed prior to this time for installing blind fasteners of the types described above. These tools have included pneumatic-hydraulic and hydraulically powered tools which use a piston to pull the stem of the fastener.
Many of these tools have suffered from the limitation that they required a source of hydraulic or pneumatic pressure to power the piston. Such a requirement adds to the cost and complexity of such equipment. Further, when a hydraulic or pneumatic pressure source is required, the tool is not portable and its use is limited only to locations where the power source is available. Furthermore, the requirement to attach a hydraulic or pneumatic source to the tool with hoses and cords prevents the tool from being used in many difficult to reach area.
More commonly, the power source is not even available in repair situations. For this type of applications, several hand powered tools have been developed. These tools typically use a hydraulically operated piston to pull the rivet stem but unlike the tools described above using hoses and cords, they utilize the operator's hand strength squeezing a lever to create the hydraulic pressure necessary to install the fastener.
One such hand operated tool is disclosed in U.S. Pat. No. 4,263,801 to Gregory which describes a relatively light and compact hydraulic hand operated riveter. This tool achieves the output force by a combination of long levers used for pumping, and a small hydraulic pump. The fluid pressure causes the piston to move away from the nose piece, which is fixed to the cylinder and engages the sleeve. As pressure in the pressure chamber increases, the piston is forced away from nose piece, at the same time pulling the stem through the sleeve and completing fastener installation.
This riveter, however, has a number of significant shortcomings, including, but not necessarily limited to, the following. First, these tools have been often bulky and heavy in comparison to their modest load capability. Second the force necessary to squeeze the lever in order to generate hydraulic pressure is often so high that it is not possible for an average person to operate the tool towards the high end of its capability, and if they do, the strain on the hand and fatigue will potentially cause the operator to stop, work very slow or even cause hand injuries. Third, the tool has low productivity as it takes a considerable amount of pumps to complete a fastener installation.
In addition to the above mentioned shortcomings, it has a narrow field of application, as it is generally dedicated to certain types of fasteners.
Another such hand operated tool is disclosed in U.S. Pat. No. 5,425,164 to El Dessouky. This tool was developed in order to overcome some of the shortcomings of the Gregory tool, and was a big improvement when first introduced.
In an initial stage, a pump plunger compresses fluid in first and second chambers into a piston chamber, causing rapid movement of the housing and drawbolt in relation to the piston, pulling the stem of a fastener in relation to its sleeve.
As the pulling force increases, and thus the necessary hand pumping force, pressure in the piston chamber opens a valve allowing the fluid in the first chamber to return to the reservoir so that only the second plunger chamber is used to compress fluid into the pressure chamber, lessening the force necessary to pump the lever.
This riveter has a number of shortcomings, as briefly stated below.
First, the tool takes too much effort to operate, which leads to rapid operator fatigue. Second, the tool has a relatively narrow field of application and pulling head change over or service is relatively difficult and time consuming. Third, the tool is very complex, hard to troubleshoot or service. Furthermore, since this tool's introduction, the ergonomic, operation and serviceability requirements for this type of tool have become more demanding, manufacturing costs have increased and newer aircraft have used stronger and more diverse fasteners requiring more installation load and versatility.
Prior art fastener setting tools thus are not fulfilling the current expectations for high productivity, versatility, simple troubleshooting and service, minimized environmental impact and advanced ergonomics like low hand effort, soft, insulated handles and adjustable tool configuration to mach the operator's hand size and strength.